Flat-plate heat-pipe with lanced-offset fin wick

ABSTRACT

A passive cooling unit for integrated electronics in form of flat-plate heat-pipe device having a shallow cavity base member, a cover plate, and a lanced-offset fin member and associated porous metal wick material sandwiched therebetween, the fin member being braced to the base member and cover plate to provide structural support and also being coated with the wick material. The resultant flat-plate heat-pipe device, when formed of a lightweight metal such as aluminum or titanium, results in a passive cooling device that is lightweight, structurally strong, and of low cost manufacture.

FIELD OF THE INVENTION

[0001] This invention relates generally to passive cooling forelectronic devices, and more particularly to a flat-plate heat-pipehaving an internal lanced-offset fin wick structure with associatedporous wick material, and a method for forming the same.

BACKGROUND OF THE INVENTION

[0002] Electronic devices such as power amplifiers, power supplies,integrated circuit chips, multi-chip modules, heat spreaders, electronichybrid assemblies such as power amplifiers, microprocessors and passivecomponents such as filters, contain heat sources which require coolingduring normal operation. Various techniques may be used for coolingelectronic devices. Traditionally, electronic devices have been cooledby natural or forced convection which involves moving air pastconduction heat sinks attached directly or indirectly to the devices.

[0003] Efforts to reduce the size of electronic devices have focusedupon increased integration of electronic components. Sophisticatedthermal management techniques using liquids, which allow furtherreduction of device sizes, have often been employed to dissipate theheat generated by integrated electronics.

[0004] Two-phase thermosyphons have often been used to provide coolingfor electronic devices. Two-phased thermosyphons typically include atwo-phase material within a housing. The two-phase material, typically aliquid, vaporizes when sufficient heat density is applied to the liquidin the evaporator section. The vapor generated in the evaporator sectionmoves away from the liquid towards the condenser. In the condensersection, the vapor transforms back to liquid by rejecting heat to theambient. The heat can also be dissipated to the ambient atmosphere by avariety of means, such as natural convection, forced convection, liquidand other suitable means. Typifying such two-phase thermosyphons is U.S.Pat. No. 6,234,242, assigned to the assignee of the present invention.

[0005] However, there are significant orientation limitations inherentin the use of such two-phase thermosyphons since they only work in avertical orientation. This is because thermosyphons need the assistancefrom gravity to get the condensed working liquid from the condensersection to the evaporator section, i.e., the condenser must always behigher than the evaporator section. Additionally, such two-phasedthermosyphon devices are not well suited for very low heat-fluxapplications.

[0006] Another cooling device often used is the so-called flat-plateheat-pipe device (“FPHP”). Such FPHP devices are suitable for lowheat-flux and medium heat-flux applications, and thus, are suitable formany electronics applications such as cellular telephonic infrastructureproducts. FPHP devices operate on the principal of a closed loop ofevaporation/boiling and condensation of a fluid. The working liquidevaporates and boils off in the areas where heat is dissipated byelectronic components, which components are mounted externally to theFPHP device's walls, and then travels to the condensation section as avapor. Contrary to the boiling occurring in two-phase thermosyphons, theevaporation in a FPHP device can advantageously occur with a very smalltemperature rise between the working liquid and the FPHP surface. Thevapor spreads evenly in the condensation space and condenses back intoliquid form by rejecting heat to the ambient, as often assisted byexternally-mounted fin structure to create a heat sink. The condensedliquid travels back to the heated section by a wicking action throughporous wick structure formed on the interior surfaces of the FPHPdevice's cover plates.

[0007] Importantly, such FPHP devices have the ability to operate in anyorientation. However, commercially available FPHP devices are typicallymade of thick-walled copper making such FPHP units extremely heavy, andtherefore impractical for most electronic cooling situations related tocellular infrastructure products. They typically use a sintered copperwick on the interior faces of the cover plate, such that no other wicksubstructure is present. Also, due to their method of manufacture,commercially available FPHP devices are very costly and relatively weak.In fact, because they are so structurally weak, they are unable towithstand high internal positive pressures or perform effectivelythroughout the broad temperature range found in many cellular and otherelectronic infrastructure products. They are generally limited tooperating when internal pressure is lower than 1 atm. Another type ofFPHP that has been typically used employs multiple cylindrical heatpipes embedded in a solid plate of aluminum. Typifying such prior FPHPdevices are U.S. Pat. No. 4,880,052, which discloses flat plates withindividual heat-pipes embedded within.

[0008] Yet a further cooling device used with integrated electronicstakes the form of an integral heat pipe, heat exchanger and clampingplate, forming a grid-like pattern of wick-lined channels, such astypified by U.S. Pat. No. 5,253,702. There, a base plate functions as anevaporator having a multiplicity of intersecting parallel andperpendicular internal channels extending across the baseplate. Asintered copper thermo wick material is applied to the surfaces of allchannels, and there is a series of vertically aligned condenser tubesforming a condenser region terminating at their upper ends in coolingfins. This is a complicated structure formed at great cost, and also hasorientation limitations to its use.

[0009] There is a need for a lightweight and compact flat-plat heat-pipecooling device that is structurally robust, thermally efficient, and hasa low cost of manufacture.

SUMMARY OF THE INVENTION

[0010] A lightweight flat-plate heat-pipe device is constructed as asealed cavity fabricated by brazing a thin, flat shallow cavity basemember with a cover plate to create a thin-shelled hollow-enclosure tocontain an evaporative working fluid. The base member includes a numberof upstanding bosses which incorporate holes for locating the fastenersused for installing external electronic circuit boards, and othermodules, on the outer surfaces of the FPHP device. A lanced-offset finstructure is affixed internally within the cavity to provide structuralsupport to the thin base member and cover plate. The lanced-offset finshave an associated porous wick structure. This overall sandwichedassembly is brazed together to provide a structurally robust sealed unithaving very thin external walls, and a small opening for theintroduction of a charge of the working fluid. The porous wick structureassociated with the lanced offset fins acts as a capillary-type wick fortransporting the condensed liquid from the condenser section back to theheated evaporator section. One end of the respective external faces ofthe FPHP unit, i.e., at the condenser section end, can be configuredwith appropriate cooling fins to convert the FPHP device into alight-weight heat-sink.

[0011] In one embodiment of the present flat-plate heat-pipe invention,the porous wick structure is flame-sprayed directly onto the lancedoffset fins. In another embodiment, the porous material is flame-spayedor otherwise applied to the internal facing surfaces of the respectivebase member and cover plate. In a final embodiment, used for heavy-dutyapplications, all of the generally transverse surfaces of thelanced-offset fins, i.e. those surfaces extending between the respectivebase member and cover plate, are encased and all open spaces packed witha sintered metal wick material to create a structurally supportiveporous wick which permits capillary movement of the working fluid in alldirections and vapor movement in the direction of the fins.

[0012] Preferably, the base member, cover plate and lanced-offset wickstructure are formed of a lightweight aluminum material or aluminumalloy. Further, the porous wicking material is preferably formed ofaluminum powder that has been flame-sprayed or sintered in place.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The means by which the foregoing and other aspects of the presentinvention are accomplished and the manner of their accomplishments willbe readily understood from the following specification upon reference tothe accompanying drawings, in which:

[0014]FIG. 1 depicts a front elevation view of the flat-plate heat-pipedevice with lance-offset fin wick structure of the present invention;

[0015]FIG. 2 is an end elevation view of the flat-plate heat-pipe deviceof FIG. 1;

[0016]FIG. 3 is a perspective view of the base member of the device ofFIG. 1;

[0017]FIG. 4 is a perspective view of the lanced-offset fin structure ofthe present invention;

[0018]FIG. 5 is an enlarged cross-sectional view, taken at circledlocation 5-5 in FIG. 8, of the present flat-plate heat-pipe deviceshowing the lanced-offset fin structure with associated porous wickmaterial, and showing circuit board structure, and with certaincomponents deleted for better viewing;

[0019]FIG. 6 is another cross-sectional view, similar to FIG. 5, but ofan alternative form of the flat-plate heat-pipe device of the presentinvention;

[0020]FIG. 7 is yet a further enlarged cross-sectional view, similar toFIGS. 5 and 6, but of yet a further alternative embodiment for theflat-plate heat-pipe device of the present invention;

[0021]FIG. 8 is a side elevation view, similar to FIG. 1, of the presentflat-plate heat-pipe device showing a circuit board includingheat-dissipating electronic devices, and a clam shell housing; and

[0022]FIG. 9 is a side elevation view of the flat-plate heat-pipe deviceof FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

[0023] Having reference to the drawings, wherein like reference numeralsindicate corresponding elements, there is shown in FIG. 1 anillustration of a flat-plate heat-pipe passive cooling device, generallydenoted by reference numeral 20. The cooling device 20 includes aflat-plate heat-pipe member 22 and external cooling fins 24, to create apassive cooling heat sink assembly. The FPHP member 22 comprises a basemember 26 and a cover plate 28. The base member comprises a base plate27, a series of upstanding support bosses or shoulders 48 (describedlater herein), and a peripheral end wall or frame 30. Collectively, thecomponents base member 26 create a shallow cavity generally denoted byreference numeral 34, which when covered off by the cover plate 28becomes a sealed enclosed cavity. The base member 26 and cover plate 28are preferably formed of a suitable aluminum material, such as analuminum-6061 alloy. The base member 26 can be machined from aluminumplate stock to yield cavity 34 and raised bosses 48. So as to create athin-shelled cooling unit 20, the wall thickness for the aluminum plates26, 28 is preferably less than 1 mm in thickness, but not less than 0.5mm thick, and preferably approximately 0.7 mm. Alternatively, instead ofusing an aluminum alloy for the base member 26, cover plate 28, and thelanced-offset fin member 36, a suitable titanium material could be used.This likewise would provide suitable structural support and rigidity toFPHP member 22, yet allow it to remain sufficiently lightweight.

[0024] An opening tube 32 (see FIGS. 1 and 7), preferably some 4.8 mm indiameter and welded along the end wall 30 (but which may also be weldedalong the baseplate 27 or cover plate 28, but not shown in eitherlocation) can be used to seal off the inner cavity 34. After thecharging process, the filler tube 32 is preferably sealed off by meansof an ultrasonic welder, which pinches and applies ultrasonic energy tothe pinched section of tube 32 to form the needed closure seal.

[0025] A lanced-offset fin member, generally denoted by referencenumeral 36, is shown in FIGS. 4-7. The lanced-offset fin member 36 ispreferably made of an aluminum material, such as an aluminum-3033 alloy,and is commercially available from vendors such as Robinson Fin Machinesof Kenton, Ohio. This lanced-offset fin member 36 has a series ofgenerally upstanding channel sections 38 and an intervening valleysections 40, with a width therebetween in the range from approximately0.5 mm to 2.5 mm, with the preferred width range of approximately 1.0 to2.0 mm. The transverse wall sections 42 integrally connecting thechannel sections 38 and valley sections 40 comprise a staggered oroffset series of walls 44 as separated by punched openings 46.Selectively cut clearance holes 47 in fin member 36 permit fin member 36to fit over and nestle around respective raised bosses 48 within cavity34.

[0026] As will be seen in FIGS. 3 and 5, the lanced-offset fin member36, while formed as a lightweight component, still creates a rigidstructural member to support the thin-walled base plate 27 and coverplate 28 particularly against the both significant internal and externalpressures that are created within enclosed cavity 34. The material wallthickness for the overall lanced-offset fin member 36 is preferably lessthan approximately 0.5 mm thick. Importantly, besides providingstructural support, the particular punched-wall configuration of thelanced-offset fin 36 presents numerous surfaces (channel sections 38,valley sections 40, and intervening wall sections 42) to support theassociated porous wick material as described below. Other configurationsfor the lanced-offset fin member 36 can include a wave-type folded fin(shaped like the corrugated layer in cardboard), lanced-offset fins likemember 36 but with inclined walls (where the vertical walls are atapproximately 120° to the horizontal walls), lanced-offset fins with afine curved pitch (where the upper and lower horizontal faces aregenerally curved surfaces instead of flat), and louvered fins (where thevertical faces of a wave-type folded fin have vertically aligned louveropenings). However, lanced-offset fin member 36 of FIG. 4 is consideredthe preferred design because that design permits the best liquid-vapormovement perpendicular to general flow direction, to provide the bestthermal performance, such vertical faces provide the best structuralstrength, and such horizontal faces provide the best high strengthbrazing bond between the fin 36 and base plate 27, cover plate 28.

[0027]FIG. 5 depicts how the lanced-offset fin member 36 is fitted intothe base member 26 and is sandwiched between the base plate 27 and coverplate 28. During manufacture, the lanced-offset fin 36 can be furthershaped by laser cut or EDM to fit into the cavity 34 of base member 26with needed clearance holes 47 to fit around the raised bosses 48. As isknown in brazing operations, a shim of suitable brazing material (notshown), such as aluminum alloy 4004 or 4104, is placed over the interiorsurface of base plate 27, and the configured lanced-offset fin 36 (withassociated porous wick material as described below), is dropped intoplace on top of the brazing material. The cover plate 28 clad with asuitable brazing material (not shown) is then placed on top of the basemember 26 and fin 36, to create a sandwiched assembly. That assembly isthen fixtured to provide uniform pressure over its entire span and thenplaced in a vacuum brazing furnace to seal the cover plate to the basemember 26, and to secure affix the fin structure 36 to the interiorsurfaces of both base plate 27 and cover plate 28. In this manner, thelanced-offset fin member 36 operates to structurally separate andstructurally support the respective base member 26 and cover plate 28 tocreate a thin-shelled flat, rigidly supported FPHP device 22.

[0028] Importantly, the use of the lanced-offset fin 36 acts toeliminate the need for having one of the base plate 27 or cover plate 28punched or dimpled for separating the base and cover plates, such as wasrequired with many prior passive cooling devices. For example, see theThermacore (Trademark) product sold under the product name Thermabase(Trademark).

[0029] The raised bosses 48 (see FIG. 3) each have an opening 50 toreceive a threaded fastener 52, which can be used to secure heatdissipating members 54 on associated circuit boards 56 to the FPHPmember 22. As seen in FIG. 7, a pair of such circuit boards 56 have beenmounted to the respective front and rear external sides of FPHP member22 via fasteners 52 engaging openings 50 in bosses 48. As seen in FIGS.7 and 8, a large number of heat-dissipating members 54 are mounted tothe respective circuit boards 56. Devices 54 can comprise poweramplifiers, power supplies, integrated circuit chips, multi-chipmodules, heat spreaders, and electronic hybrid assemblies such as powersupplies, microprocessors and passive components such as filters. All ofthese electronic devices contain heat sources which require coolingduring normal operation.

[0030] As seen in FIG. 2, the FPHP member 22 can have cooling fins 28mounted to both external surfaces at the upper end thereof to form acomplete heat sink assembly. This acts to divide the FPHP unit 22 intogenerally an evaporator section 58 and a cooling or condensing section60. Alternatively, simply the FPHP member 22 can be used alone, i.e.,without external cooling fins 24, by having the member's condensingsection 60 of member 22 in contact with a chassis (not shown) whichconducts rejected heat away, such as with a thermal backplane device.

[0031] Turning to FIG. 4, the various external surfaces of thelanced-offset fin member 36 (comprising channel sections 38, valleysections 40, and transverse punched wall sections 42) have anappropriate porous metal wicking material, generally denoted byreference numeral 62, applied thereon. The porous metal wicking material62 forms a porous wick structure to transport fluid medium therealong,and is supported by fin member 36. Material 62 preferably comprises aporous aluminum foam coating, such as powdered aluminum which has beenpreferably flame-sprayed onto the fin member 36. Advantageously, use ofa flame-spraying application method results in a uniform layered coatingof wick material 62. The porous wicking material layer 62 is preferablybetween approximately 1.0 and 2.0 mm thick. Such a porous aluminumwicking material 62 acts as an excellent capillary-type wick to conveythe condensed working liquid (such as an evaporative liquid medium; notshown) from the condenser section 60 along the lanced-offset fin member36 to the evaporator section 58. As an alternate material to use for theporous wicking material 62, it could instead be formed as a sinteredcopper or sintered bronze material. Either such alternate material canbe suitably flame-sprayed or otherwise applied to the lanced-offset finmember 36 to again create a suitable wicking structure for FPHP member22.

[0032] Due to the presence of the porous wicking material 62 asflame-sprayed onto the lanced-offset fin member 36, the present FPHPcooling unit 20 can be utilized in any orientation. That is, the presentinvention's FPHP device 20 is not gravity-dependent, such as were theprior art FPHP and two-phase thermosyphon devices which were alwaysrequired to be oriented vertically. Thus, such an“operable-in-all-orientations” feature is a significant improvement overthe previously available passive cooling products. In sum, besidesacting as a structural support for the base plate 27 and cover plate 28,the lanced-offset fin member 36 further acts as a structural support forthe wick surface formed of porous wicking material 62 inside the innercavity 34 of the FPHP member 22.

[0033] Referring to FIGS. 1 and 3, using suitable evacuation equipment,the inner shallow cavity 34 can be evacuated via the opening tube 32.Then the desired amount of a suitable working fluid medium, such asacetone, can be introduced through opening tube 32. Once the evaporativeliquid medium has been introduced into inner cavity 34, the opening tube32 can be closed, such as by pinching off opening tube 32, ultrasonicwelding, or some other suitable method to seal off filler tube 32 andthe inner cavity 34 thereby retaining the working medium within the FPHPmember 22. Alternatively, instead of using an aluminum alloy for thebase member 26, cover plate 28, and the lanced-offset fin member 36, asuitable titanium material could be used. This likewise would providesuitable structural support and rigidity to FPHP member 22, yet remainsufficiently lightweight.

[0034] An alternate embodiment of the present invention is depicted inFIG. 6, where like reference numerals are used for like structuralelements relative to the preferred embodiment of FIG. 5. That is, inFIG. 6, the porous wicking material 62 is shown, instead of beingapplied directly on the lanced-offset fin member 36, as beingflame-sprayed onto the interior facing surfaces of the respective baseplate 27 and cover plate 28. Thus, in this embodiment there is no porouswicking material 62 present on the lanced-offset fin member 36 at all.Otherwise, this alternate embodiment FPHP member 22′ of FIG. 6 isidentical to the FPHP member 22 of the preferred embodiment depicted inFIG. 5.

[0035] Depicted in FIG. 7 is yet a further alternative embodiment of thepresent invention, generally denoted by a reference numeral 22″. Here,the associated porous wicking material 62 is so formed and configuredthat the material 62 encases, and packs all open spaces, around thewalls 44 of punched wall sections 42, upstanding channel sections 38,and intervening valley sections 40 of lanced-offset fin member 36. Thus,while no porous wicking material 62 is present or formed directly on theinner surfaces of base plate 27 and cover plate 28 so that appropriatebrazing occurs, nevertheless there is a substantially larger amount ofthe porous wicking material 62 present and structurally supported by thelanced-offset fin member 36 in this FIG. 7 embodiment than with theprior two embodiments (of FIGS. 5 and 6).

[0036] The specific configuration for the porous wicking material 62found in the embodiment of FIG. 6 is formed by utilizing a pair ofstainless steel plates with inwardly-protruding, mating linear fins(none shown) to sandwich the lanced-offset fin member 36 therebetween.The remaining open spaces are packed with a suitable powdered metalmaterial, and then sintered in a furnace. A porous aluminum powderedmetal can be used. Then, once suitably adhered to the lanced-offset finstructure 36, the porous wick structure is created with the sinteredpowdered metal being heat fused together but still essentially retainingto same pore geometry as previously present between the powdered metalparticles. The stainless steel plates (not shown) are then removed toresult in an integral assembly of lanced-offset fin 36 with sinteredwick structure (formed of porous wick material 62) as shown in FIG. 6.Importantly, the surfaces of the lanced-offset fin 36 that face and matewith the base plate 27 and cover plate 28 are free of porous wickmaterial 62, thus allowing a very high strength braze joint between thesame. The resulting sintered metal wick structure allows X-Y-Z movementof condensed fluid throughout the structure, while vapor moves in theopen areas where the stainless steel fins were during sintering. Due tothis particular metal wick structure, a very strong FPHP device 22 iscreated that is capable of withstanding significant internal andexternal pressure, e.g., greater than 500 psig.

[0037] It will be understood that the specially-configured sinteredmetal wick and lanced-offset fin assembly described above for thisalternate embodiment of FIG. 7 can also be beneficially used in theheavy-walled copper type FPHP's of the prior art, so as to reduce theiroverall resultant weight and cost.

[0038] In FIG. 8 is shown a suitable clam shell-type cover housing 64,which is used to cover off and protect the respective circuit boards 56and heat dissipating members 54 carried thereon from externalenvironment and potential damage. As needed, the cover housing 64 can bereadily removed for suitable installation or repair purposes. Housing 64can be formed as a cast aluminum or cast magnesium component.

[0039] The present FPHP cooling devices are thin-shelled units withlanced-offset fin structure brazed to both cover plates, resulting in astructurally strong sealed unit. They can, for example, be some 406 mm(16 inches) by 254 mm (10 inches) in size. It provides significantweight, size and cost savings over the prior two phase thermosyphons,and prior heavy, thick-walled copper-clad FPHP devices. The presentpassive cooling FPHP devices are particularly useful in cellular basestation equipment, personal computers, supercomputers, power supplies,automotive electronic, and communication infrastructure equipment, e.g.,microsite and picosite cellular equipment. The present invention allowsuse of a low cost passive cooling system in such electronicsapplications, reduces overall permissible product size and weight, andthus allows a higher overall electronics package density for the enduser.

[0040] From the foregoing, it is believed that those skilled in the artwill readily appreciate the unique features and advantages of thepresent invention over previous types of passive cooling units forintegrated electronic devices. Further, it is to be understood thatwhile the present invention has been described in relation to aparticular preferred and alternate embodiments as set forth in theaccompanying drawings and as above described, the same nevertheless issusceptible to change, variation and substitution of equivalents withoutdeparture from the spirit and scope of this invention. It is thereforeintended that the present invention be unrestricted by the foregoingdescription and drawings, except as may appear in the following appendedclaims.

We claim:
 1. A flat-plate evaporative-fluid type passive cooling devicefor use in dissipating heat in electronic applications, comprising incombination: a base member having a shallow cavity formed internallytherein, said cavity including a plurality of upstanding support bossmembers; a cover plate adapted to sealably close off said base member toenclose said shallow cavity to enable containing an evaporative fluidmedium therewithin; lanced-offset fin means fitted into said shallowcavity and adapted to support said cover plate and said base memberagainst external and internal pressure; and porous metal wick meansassociated with said lanced-offset fin means and adapted to permit theevaporative fluid medium to travel therealong by capillary action oncecondensed from an evaporative state.
 2. The device of claim 1, whereinsaid base member comprises a base plate portion, said plurality ofupstanding bosses are formed on said base plate portion, and aperipheral wall portion extends from said base plate portion to formsaid shallow cavity within said base member.
 3. The device of claim 1,and wherein said lanced-offset fin means, said base member, and saidcover plate are formed of metallic material and said lanced-offset finmeans are affixed to said base member and said cover plate by brazing.4. The device of claim 3, wherein said porous metal wick means comprisea powdered metal coating applied directly onto said lanced-offset finmeans.
 5. The device of claim 4, wherein said applied coating of saidpowdered material is a flame-sprayed coating.
 6. The device of claim 4,wherein said applied coating covers all non-brazed surfaces of saidlanced-offset fin means.
 7. The device of claim 2, wherein said porousmetal wick means is applied onto the interior surfaces of said baseplate and said cover plate.
 8. The device of claim 3, wherein saidporous metal wick means is formed as a sintered metal enclosure coveringall non-brazed surfaces of said lanced-offset fin means, whereby saidsintered metal enclosure permits the evaporative fluid medium to travelby capillary action in all directions once condensed from an evaporativestate.
 9. The device of claim 1, and filler opening means adapted topermit evacuation, filling, and sealing of said enclosed shallow cavity.10. The device of claim 3, wherein said metallic material is formed fromone of aluminum and an aluminum alloy.
 11. The device of claim 1, andwherein said porous metal wick means is formed of aluminum powder. 12.The device of claim 1, wherein said porous metal wick means comprisesflame-sprayed aluminum powder.
 13. The device of claim 1, wherein saidporous metal wick means is from approximately 1.0 mm to 2.0 mm thick.14. The device of claim 2, wherein said base plate portion and saidcover plate are each from approximately 0.5 mm to 1.0 mm thick.
 15. Thedevice of claim 1, and extended cooling fin means affixed to the outersurfaces of at least one end of said respective base member and saidcover plate to permit external heat sink dissipation of heat collectedand released during condensation of said evaporative fluid medium. 16.The invention of claim 3, wherein said metallic material is formed fromone of titanium and a titanium alloy.
 17. A method for providing passivecooling for integrated electronic devices, comprising the steps of: a)forming a shallow-cavity metal base member having a base plate member, aperipheral wall member, and a plurality of upstanding support bossmembers; b) fitting a lanced-offset metallic fin member into the shallowcavity base member; c) installing porous metal wicking material intosaid shallow cavity base member; d) enclosing the shallow cavity byaffixing a cover plate to the base member; e) brazing the lanced-offsetmetallic fin member to both the base member and the cover plate; f)forming a fitting opening for the enclosed shallow cavity; g) evacuatingthe interior of the enclosed shallow cavity through the fitting opening;h) introducing a quantity of evaporative liquid medium into the enclosedshallow cavity through the fitting opening; and i) sealing off thefitting opening.
 18. The method of claim 17, and the step of forming theshallow cavity base member, cover plate, and lanced-offset metallic finmember of aluminum.
 19. The method of claim 1, and the step of formingthe porous metal wicking material of aluminum powder.
 20. The method ofclaim 19, and the step of flame-spraying the aluminum powder.
 21. Themethod of claim 17, and the step of applying said porous metal wickingmaterial onto the surfaces of the lanced-offset metallic fin member. 22.The method of claim 17, and the step of applying said porous metalwicking material onto the interior surfaces of the base plate member andcover plate.
 23. The method of claim 17, and the step of encasing theportions of the lanced-offset fin member which as extend between thebase plate member and cover plate with the porous metal wickingmaterial.
 24. The method of claim 23, and the step of forming theencasement of porous metal wicking material about the lanced-offset finmember by fixturing the fin member between metal plates formed withdepending linear fins, filling the voids between the metal plates andwithin and surrounding the exposed surfaces of the lanced-offset finmember with a metal powder, sintering the metal powder to thelanced-offset fin member by heating, and removing the metal platemembers.